Generally, a fuel cell system is composed of a fuel cell stack that generates electrical energy, a fuel supply system that supplies fuel (hydrogen) to the fuel cell stack, an air supply system that supplies oxygen from the air to the fuel cell stack as a oxidant needed for the electrochemical reactions, a thermal and water management system that controls the operating temperature of the fuel cell stack, and the like.
A hydrogen tank included in the fuel supply system, i.e. the hydrogen supply, stores compressed hydrogen under a high pressure of about 700 bars, and after this stored compressed hydrogen is discharged to a high-pressure line according to the on/off manipulation of the high-pressure controller mounted at the entrance part of the hydrogen tank, it is decompressed as it passes through the starting valve and the hydrogen supply valve, before it is supplied to the fuel cell stack.
Here, a high-pressure gas is used as fuel (hydrogen), and as such, there is a need for a gas storage container for storing and discharging the gas as needed. In particular, since gases have a low storage density within a container, it is most efficient to store a gas under high pressure, although there is the drawback that the high pressure creates a risk of combustion. In particular, an alternative-fuel gas vehicle has a limited amount of space for a storage container, and as such a key technological element is to keep the storage pressure high while guaranteeing safety.
Therefore, in the case of a composite-material container for storing fuel gas, the outer skin must be reinforced with a fiber-reinforced composite material having high specific strength and high specific stiffness in order to withstand the high internal pressure from the hydrogen gas, and a liner is installed on the inside to maintain airtightness. More specifically, a liner having two semispherical forms at both ends may be attached to form one storage container.
In addition, containers for storing gas, especially hydrogen, may be classified into different types according to the material of the liners, with containers having liners of metallic materials classified as Type 3 and containers having high-density polymer materials classified as Type 4. Type 3 containers are relatively stable but are expensive and have low fatigue resistance, while Type 4 containers are relatively inexpensive and have better fatigue resistance but entail safety-related problems associated with hydrogen leakage, low impermeability, etc.
In particular, high levels of stress occur along the circumferential direction at the cylinder part formed at the center of a high-pressure container. Thus, there is a need for a composite layer structure that winds around the cylinder part of a high-pressure container to withstand the stresses applied thereon, as well as for technological features that allow reduced weight while providing resistance to high levels of stress.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.